Soil engineering by ants facilitates plant compensation for large herbivore removal of aboveground biomass

The interplay between top-down and bottom-up processes determines ecosystem productivity. Yet, the factors that mediate the balance between these opposing forces remain poorly understood. Furthering this challenge, complex and often cryptic factors like ecosystem engineering and trait-mediated interactions may play major roles in mediating the outcomes of top-down and bottom-up interactions. In semi-arid grasslands of northeastern China, we conducted a large-scale, three-year experiment to evaluate how soil engineering by ants and plasticity in plants independently and jointly influenced the top-down effects of grazing by a ubiquitous herbivore (cattle) on aboveground standing biomass of the dominant perennial grass, Leymus chinensis. Herbivory had strong top-down effects, reducing L. chinensis AB by 25% relative to baseline levels without cattle or ants. In contrast, soil engineering by ants facilitated weak bottom-up effects in the absence of herbivory. However, in the presence of her...下行控制（top-down）与上行控制（bottom-up）过程的相互作用决定了生态系统生产力。然而，调控这两种对立调控过程间平衡的因子，目前仍未得到充分阐释。这一难题进一步复杂化，因为诸如生态系统工程（ecosystem engineering）与性状介导的相互作用（trait-mediated interactions）这类复杂且往往难以捉摸的因子，可能在调控下行与上行控制相互作用的结果中发挥关键作用。本研究在中国东北半干旱草原开展了一项为期三年的大规模野外实验，旨在探究蚂蚁的土壤工程作用与植物表型可塑性分别以及共同如何影响广布植食动物——牛的放牧所产生的下行控制效应，及其对优势多年生草本植物羊草（Leymus chinensis）地上现存生物量的作用。植食作用表现出显著的下行控制效应：相较于无牛与无蚂蚁的对照组基线水平，羊草的地上生物量降低了25%。与之相反，在无植食作用的条件下，蚂蚁的土壤工程作用仅能引发微弱的上行控制效应。然而，在存在植食作用的条件下……